In working on some recent research, I ran into the classic 1927 map from Paramount Studios showing filming locations in California (reproduced in numerous works):
Add this to the capabilities of shooting on backlots and the world may be relatively easy to access from Hollywood. There are likely other reasons the film and television industry chose to locate together in and around Hollywood but having such varied nearby locations likely helps.
One thing that is missing from this map: urban locations. This map certainly reflects an interest in more natural settings. Los Angeles in 1927 was still under development. Even later Los Angeles can be fairly distinctive – just look at all the car ads filmed in and around the city. San Francisco offers some spectacular scenery but its uniqueness means it could be hard for the location to double for other places.